Ionene polymers, i.e., cationic polymers containing quaternary nitrogens in the polymer backbone, are known to be useful in controlling bacteria and algae in various aqueous systems. U.S. Pat. Nos. 3,874,870; 3,931,319; 4,027,020; 4,089,977; 4,506,081; 4,581,058; and 4,111,679 give various examples of these polymers. The disclosures of these patents are incorporated specifically by reference herein.
One such polymer is poly[oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride]. This polymer is manufactured and sold by Buckman Laboratories Inc. under the names Busan.RTM. 77 and WSCP.RTM. as a biocide used primarily in aqueous systems, including concentrates of metalworking fluids for microorganism control.
Another such product is the ionene polymer produced by the condensation of equimolar amounts of dimethylamine and epichlorohydrin, as disclosed in U.S. Pat. No. 4,111,679.
Synergistic combinations of ionenes and hexahydro-1,3,5tris(2-hydroxyethyl)-s-triazine, however, do not appear to be known in the literature.
Both of these types of products are used alone to control microorganisms in industrial settings. Many industries experience problems caused by microorganisms. These problems are especially present where aqueous systems are used. The machining industry is one such industry in which problem-causing microorganisms are encountered. In machining operations, metalworking fluids are used primarily to reduce friction and heat, thereby reducing wear and prolonging the life of equipment.
Unfortunately, metalworking fluids have many properties which make them an ideal medium for the growth of bacteria and fungi. These microorganisms can cause such problems as: the buildup of slime/microbial deposits on machine surfaces, the clogging of jets and lines, the deterioration of the properties of the metalworking fluid itself, enhanced corrosion, as well as health and odor problems. Although bacteria are important in the biodeterioration of cutting fluids, fungi and yeast play an important role as well, especially in synthetic fluids. (Bennet, E. O., "The Deterioration of Metalworking Fluids", Prog. Industrial Microbiology, 13:121 (1974)).
As microorganisms grow in the metalworking fluid, the fluid begins to deteriorate and loses many of its essential properties. Its pH may drop and other chemical changes may occur until the fluid no longer is able to provide adequate lubrication. At this point, the fluid must be replaced with fresh fluid. This is costly and results in loss of production time.
The previously mentioned problems have resulted in the extensive use of biocides in metalworking fluid systems. Biocides may be incorporated in fluid concentrate or added to diluted fluids once they are in the holding tanks of the machine works.
There are many commercially available biocides used today. Each of these biocides is generally useful, but each is attended by a variety of impediments. Some biocides have odor problems, or create hazards with respect to storage, use or handling, which limit their utility. Presently, no one type of compound has significantly overcome any of the problems mentioned.
Economic factors should be considered before choosing a particular biocide for use in metalworking fluid systems. Such economic considerations apply to both the cost of the biocide and the expense of its application. The cost performance index of any biocide is derived from the basic cost of the material, its effectiveness per unit weight, the duration of its biocidal or biostatic effect in the system treated, and the ease and frequency of its addition to the system treated.
At present, none of the commercially available biocides is capable of exhibiting a prolonged biocidal effect. Instead, physical conditions, such as temperature and chemical reactivity with ingredients present in the system, often diminish or eliminate the effectiveness of the biocides. For example, many systems contain organic material which may react with a specific biocide or render it ineffective.
Hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine has been used in the metalworking fluid industry for a long time. As can be seen in Table I, high concentrations of this compound are required to control both bacterial and fungal growth in metalworking fluids. One of the by-products of the hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine is formaldehyde. Because of the carcinogenic properties of formaldehyde, it is desirable to use compounds that produce formaldehyde in the smallest quantities possible.
Metalworking fluid systems in which heavy microbial growth occurs would benefit from the practice of the present invention, which is described below. The practice of the present invention would also benefit many other systems, whether or not heavy microbial growth occurs, because it provides a more limited use of hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine, a formaldehyde producing biocide.